The invention is directed to a controllable optical directional coupler formed of two strip waveguides integrated on a substrate of semiconductor material, as proposed in the earlier German Patent Application P 39 29 131.6 (GR 89 P 1730 DE), incorporated herein.
In the proposed directional coupler, the pn-junction or pin-junction extends over the entire length of the two strip waveguides designed as rib waveguides. These strip waveguides thus have a uniform waveguide structure, whereby the pin-junction is electrically controllable via electrical contacts only in the coupling section.
This directional coupler can be operated as an optical switch which supplies an optical input signal to the one or to the other output of the switch, depending on an electrical control signal.
In the proposed directional coupler, the function of this component is generally dependent on the polarization of the input signal, i.e. TE-polarized input signals are distributed differently onto the outputs than TM-polarized input signals with a given geometry.